A COMPARISON OF THE WETTABILITY OF COPPER-COPPER OXIDE AND SLIVER-COPPER OXIDE ON POLYCRYSTALLINE ALUMINA

The contact angles of liquid silver-copper oxide/alumina and liquid copper-copper oxide/alumina systems were determined using the sessile drop method. Copper oxide (CuO) additions of 1.5-10.0 wt% were made. Temperatures of 970-1250 degrees C for the silver-based alloys and 1090-1300 degrees C for the copper-based alloys were studied. Minimum contact angles of 42+/-8 and 64+/-7 degrees were obtained for the copper-copper oxide alloys and the silver-copper oxide alloys, respectively. The contact angle was approximately constant for the silver-copper oxide alloy within the immiscible liquid composition range. While the contact a ng les were higher for the silver-based alloys relative to the copper-based alloys, successful infiltration of a porous alumina sample was achieved at only 1050 degrees C for a Ag-10 wt% CuO alloy. Compression tests on infiltrated samples revealed similar compressive strengths for alumina samples infiltrated with silver-copper oxide alloys, silver-copper-copper oxide alloys and copper-copper oxide alloys. The compressive fracture strength for the infiltrated samples was an order of magnitude higher than the fracture strength of the porous alumina body without infiltration. Although silver-based alloys are more expensive than comparable copper-based alloys, in many applications the additional cost may be offset by lower processing or brazing temperatures, improved thermal and electrical conductivity, and improved toughness.